1. Field of the Invention
The present invention relates to a switching device for selecting an operational instruction and deciding the operational instruction, and more particularly to a switching device that exhibits a decrease in malfunctions.
2. Description of the Related Art
For example, in a portable telephone system, key operation becomes disadvantageously complicated with recent progress of soft function, and moreover, density of keys in accordance with downsizing of the body as well as miniaturization of the key itself further make the operation complicated. In order to cope with these problems, various techniques of a switch have been proposed, such as a switch in a combination of a function key and a numeric key, using a jog dial, using a cross key, and using a stick switch.
For example, in the case of using a stick switch, one key operation enables a shift of a cursor for retrieving an operational instruction and executing the retrieved operational instruction, thereby improving the operational performance remarkably compared with the case of pressing a numeric key many times. In the structure of separately mounting a stick switch (for example, a purchase), however, since volume for the body of the stick switch itself and area for soldering it are required, in advancing downsizing and thinning of the portable telephone system, the size of a stick switch may be disadvantageously limited and a malfunction may easily occur.
In place of this stick switch, for example, Japanese Patent Application Laid-Open Publication No. 11-126126 discloses a scroll switch device for a portable telephone, comprising a decision switch for deciding an operational instruction of a portable telephone and a plurality of selection switches for shifting a cursor on an information display. This scroll switch device, however, does not sufficiently prevent a malfunction from occurring.
As mentioned in the above conventional example, even a scroll switch device having a much greater possibility of being downsized, relative to a stick switch, is defective in preventing a malfunction from occurring. Therefore, a switch that is capable of surely preventing a malfunction is highly desired.
In order to solve the above conventional problem, the present invention aims to provide a switching device that decreases the possibility of a malfunction occurring when selecting an operational instruction by a selection switch and deciding the operational instruction by a decision switch.
In order to achieve the above object, a switching device according to the present invention comprises a decision switch for deciding an operational instruction, a selection switch disposed around the decision switch for selecting an operational instruction, a key top whose central portion is disposed over the decision switch, and a guide disposed around the key top. The switching device is constructed such that pressure applied to a central portion of the key top is transmitted to the decision switch, and a force resulting from tilting of the key top away from a central axis is transmitted to the selection switch through the guide. Also, the key top and the guide are separately formed with an interstice provided therebetween.
Accordingly, since the interstice is provided between the key top and the guide, the pressure applied to the central portion of the key can be prevented from being transmitted to the selection switch when this pressure is to be transmitted only to the decision switch, even when the key top is slightly tilted. Accordingly, such a malfunction in which the selection switch is also operated during operation of the decision switch is prevented.
A switching device according to the present invention comprises a decision switch for deciding an operational instruction, a selection switch disposed around the decision switch for selecting an operational instruction, and a key top whose central portion is disposed over the decision switch. The switching device is constructed such that pressure applied to the central portion of the key top is transmitted to the decision switch, and a force resulting from tilting of the key top away from a central axis is transmitted to the selection switch. The decision switch and the selection switch are each formed as a domed switch for switching, through conducting electricity, between isolated conductive terminals in response to pressure applied to a curved protruded elastic material. Also, the decision switch is formed as a domed switch of more layers than the selection switch.
Accordingly, since the decision switch is formed as a domed switch having more layers than the selection switch, the decision switch becomes difficult to be pushed down as compared to the selection switch. Therefore, even if a force in the downward direction (that is, in the direction of the decision switch) is produced when the force resulting from tilting of the key top away from the central axis is transmitted to the selection switch, the decision switch can be prevented from being depressed. In other words, such a malfunction in which the decision switch is also depressed when the selection switch is depressed, can be prevented.
Additionally to the above structure, a switching device according to the present invention further comprises a key base disposed between both switches (namely, the decision switch and the selection switch) and the key top. This switching device is constructed such that pressure applied to the central portion of the key top is transmitted to the decision switch through the key base, and the force resulting from tilting of the key top away from the central axis is transmitted to the selection switch through the key base. Also, a through hole is provided in a part of the key base between the portion corresponding to the upper portion of the decision switch and the portion corresponding to the upper portion of the selection switch, thereby making this part weaker than other portions of the key base.
Accordingly, since the part of the key base between the portion corresponding to the upper portion of the decision switch and the portion corresponding to the upper portion of the selection switch is weaker than other portions of the key base, the pressure applied to the central portion of the key top becomes difficult to be transmitted to the selection switch, and the force resulting from tilting of the key top away from the central axis becomes difficult to be transmitted to the decision switch, thereby preventing such a malfunction in which the other of the decision switch and selection switch is also operated during operation of a selected one of the decision switch and the selection switch.
A switching device according to the present invention comprises a decision switch for deciding an operational instruction, a selection switch disposed around the decision switch for selecting an operational instruction, a key top whose central portion is disposed over the decision switch, and a key base disposed between both switches (namely, the decision switch and the selection switch) and the key top. This switching device is constructed such that pressure applied to the central portion of the key top is transmitted to the decision switch through the key base, and the force resulting from tilting of the key top toward a central axis is transmitted to the selection switch through the key base. Also, the selection switch and the key base are adjacently provided, while an interstice is provided between the decision switch and the key base.
Accordingly, since the selection switch and the key base are adjacently provided and an interstice is provided between the decision switch and the key base, the decision switch becomes more difficult to be operated than the selection switch while the force resulting from tilting of the key top is being applied, thereby preventing such a malfunction in which the decision switch is also operated during operation of the selection switch.
Additionally to the above structure, a switching device according to the present invention is constructed such that the part of the key base between the portion corresponding to the upper portion of the decision switch and the portion corresponding the upper portion of the selection switch is weaker than other portions of the key base. Especially, a switching device according to the present invention is preferably constructed such that a through hole is provided in the key base between the portion corresponding to the upper portion of the decision switch and the portion corresponding to the upper portion of the selection switch, thereby making this part weaker than the other portions of the key base.
Accordingly, since the part of the key base between the portion corresponding to the upper portion of the decision switch and the portion corresponding to the upper portion of the selection switch is weaker than the other portions of the key base, the pressure applied to the central portion of the key top becomes difficult to be transmitted to the selection switch, and the force resulting from tilting of the key top away from the central axis becomes difficult to be transmitted to the decision switch, thereby preventing such a malfunction in which the other of the decision switch and selection switch is also operated during operation of a selected one of the decision switch and selection switch.
Additionally to the above structure, a switching device of the present invention is constructed such that the decision switch and the selection switch are formed on a key sheet, and this key sheet and the key base are integrally formed with the key sheet and the key base of each numeric key.
Accordingly, since the both switches (namely, the decision switch and the selection switch) and the numeric key use the key sheet and the key base in common, a reduction in the number of the parts along with a reduction in cost, and downsizing and thinning of the switching device can be realized.
Further, a portable terminal device provided with one of the above-mentioned various switching devices can be provided.
The portable terminal device provided with a switching device capable of selecting an operational instruction and deciding an operational instruction, as mentioned above, can prevent a malfunction during operation of the switching device.